Question

我正在学习Java中的正则表达式（技术上是Android API）并且遇到了一个问题。我最初使用的是Java String.matchAll(String expression, String occurence);的基本功能，但现在我使用了Pattern和Matcher类。

我跟着this tutorial学习基础知识，看起来很简单。

我的Java正则表达式是info(.*?)\\,，我也试过了：(?<=\\binfo\\=).*?(?=\\=)。

对于第一个正则表达式，如果我有一个字符串"info i = 5,"，它将解析为"info = 5"。对于第二个，如果使用相同的字符串，我会得到一个没有匹配的例子（我认为是InputMismatchException）。

我的解析代码是：

//Produces "info i 5" rather than the desired "i"
public String parseStringAlias(String textToBeParsed)
{
    //Gets the value(or alias) located between the word info and the = sign
    Pattern p = Pattern.compile("info(.*?)\\=");
    Matcher m = p.matcher(textToBeParsed);

    //0 would be the first match
    return m.group(0);
}

//Returns InputMismatchException rather than the desired number between equals sign and comma
//If given out example of "info i = 5," should return 5
public String parseStringValue(String textToBeParsed)
{
    //Pattern fetches the value between the "=" and the ","
    Pattern p = Pattern.compile("(?<==).*?(?=\\,)");

    //Search for matches
    Matcher m = p.matcher(textToBeParsed);

    //0 would be the first match
    return m.group(0);
}

Answer 1

你的正则表达式存在一些问题：你应该只使用(而不是{{)转义特殊的正则表达式字符，例如[，\\，//等。 1}}而不是像,或=这样的字符。

您没有匹配任何内容，因为您没有“运行”正则表达式搜索。

在每个返回行之前添加m.find()，更好，在if中使用它。看起来您正在使用.group(1)方法寻找parseStringAlias值：

public static void main (String[] args) throws java.lang.Exception
{
    System.out.println(parseStringAlias("\"info i = 5,\""));
    System.out.println(parseStringValue("\"info i = 5,\""));
}
//Produces "info i 5" rather than the desired "i"
public static String parseStringAlias(String textToBeParsed)
{
    //Gets the value(or alias) located between the word info and the = sign
    Pattern p = Pattern.compile("info(.*?)="); // <- Note removed `//`
    Matcher m = p.matcher(textToBeParsed);
    //0 would be the first match
    if (m.find()) {                          // < - We "ran" the regex search
        return m.group(1);                   // <- Group 1 is accessed
    }
    return "";
}   

//Returns ImputMismatchException rather than the desired number between equals sign and comma
//If given out example of "info i = 5," should return 5
public static String parseStringValue(String textToBeParsed)
{
    //Pattern fetches the value between the "=" and the ","
    Pattern p = Pattern.compile("(?<==).*?(?=,)");          // <- Note removed `\\` and `//`
    //Search for matches
    Matcher m = p.matcher(textToBeParsed);
    //0 would be the first match
    if (m.find()) {                               // <- We "ran" the regex
        return m.group(0);                       // <- We access 0th group, the whole match
    }
    return "";
}

请参阅IDEONE demo

如何在单词和等号以及等号和值之间获取文本？

1 个答案: